Valid.
They do not say how they intend to power what is essentially a low flying plane so I was making the assumption of a turbine. Electrified rails or an overhead wire did not seem practical for something intended to fly.
With a turbine you eliminate the need for a route long power source and theoretically you reduce the maintenance costs to maintaining the train its self and the containment walls and not hundreds of miles of electrified wire or track. A turbine engine also eliminates the problem Japan saw where the March earthquake knocked out power and trains were stranded. Only to be hit by the tsunami minutes later.
Bio fuels instead of oil products, as demonstrated by the US Air Force and several airlines, can also fuel turbines so it becomes sustainable. Potentially they could grow some of their own fuel in the railroad rights of way while providing a barrier for people concerned about the noise from trains running in excess of 200 mph close to their homes.
With this design if you do not eliminate the electric power infrastructure you would be looking at higher maintenance / operating costs because you would have to maintain the containment walls and the power grid.
Keep in mind that Europes long praised train system built its reputation around diesel electric trains running affordably at speeds up to 120 mph. I am not sure when the obsession with electric HSR began, but ever since the Europeans went electric their rail systems have been bleeding money and requiring subsidies to operate. Beyond their use in flying trains, turbines might be the natural evolution from diesel electric engines.
Another potential design / safety feature of this is putting the train in trenches to limit noise and improve access control. Beyond being sturdier than walls, they would make it easier to run the train under road crossings and limit other types of unintended access. The trench option would allow for simple roof structures to be put in place over the trenches to manage most weather situations.
I say trenches because you really do not need to spend the money on tunnels when covered surface trenches will do the trick at a fraction of the costs.
